Circulating Peripheral Blood Mononuclear Cells from Adults with Sickle Cell Disease (SCD)- Associated Pulmonary Hypertension (PH) Patients Have Increased Iron Content and a Unique Multi-Omic Signature

Introduction: The prevalence of PH in the SCD adult population is 6-10%, compared to approximately 3 in one million in the general population. However, the molecular mechanisms are not clearly defined, particularly as they relate to the onset and progression of SCD-PH. Previously, we have shown an accumulation of pulmonary vascular macrophages (Mϕ), iron, and hemoglobin (Hb) in SCD-PH, suggesting that hemolysis-mediated iron-overloading is a pathological contributor to progressive pulmonary vascular disease with SCD patients. Hypothesis: Here we hypothesized that PBMCs in SCD-PH patients will have a higher iron content and express a different proteomic and metabolomic landscapes than PBMCs collected from adults with other etiologies of PH and SCD without PH. Methods: PBMCs were analyzed for iron content and multi-omics analysis from six (n=6) SCD-PH (PH^SCD), ten (n=10) PH without SCD (PH), and twenty two (n=22) SCD no PH patients (SCD). Results: ICP analysis revealed that PBMCs from PH^SCD and SCD patients had greater iron concentration then PH patients. Proteomics captured a total 6,487 proteins from PBMCs isolated from PH^SCD, PH, and SCD patients. Remarkably, 2,251proteins were significantly altered between PH^SCD and PH patients (p-value £ 0.05), including 209 proteins associated with completement, 38 proteins coupled with inflammation, 163 proteins linked from idiopathic PH, and 48 proteins correlating to iron. Using the top 100 differentiated proteins, network analysis showed a significant increase in cellular macromolecule catabolic processes. Metabolic analysis depicted a decrease in alpha linolenic acid (ALA) metabolism and an increase in purine metabolism, but not purine recycling. ALA metabolism has been shown to be antioxidant and anti-inflammatory. In contrast, comparing PH^SCD to SCD just 204 proteins (9%) were significantly altered; 90% less than in PH (p<.05). Importantly, this includes SAMD14, a protein known to be involved in stressed-dependent erythropoiesis. The top 100 differentiated proteins were used for network analysis and were shown to highly correlate with positive regulation of transcription. Metabolomic differences were not as well clustered as the proteomic differences. Most metabolites were decreased and were highly correlated with the Warburg Effect and glycolysis. Conclusion: The results support the hypothesis that PBMCs from adults with SCD-associated PH differ from those with other etiology-associated PH and even the greater SCD population. Further, the relative similar PBMC phenotype observed between SCD-PH and SCD patients (as compared to PH patients) may suggest why SCD patients are at such a high risk of developing PH.

George:Agios: Consultancy.